Optical filter, production method for this optical filter and optical device using this optical filter and housing structure for this optical filter

ABSTRACT

An optical low pass filter is constituted by a quartz birefringent plate a quarter wavelength plate and a quartz birefringent plate layered in that order. Curved chamfered portions are formed at a periphery of an outgoing light surface (main surface) of one of the quartz birefringent plates. A curve chamfering width of a main surface side is smaller than that of a side surface side.

TECHNICAL FIELD

The present invention relates to optical filters made of one or moreoptical plates, methods of manufacturing such optical filters, opticaldevices that use such optical filters, and storage structures for suchoptical filters.

BACKGROUND ART

Various optical filters such as optical low pass filters are used inimage-taking devices such as video cameras and digital still cameras.Such filters perform a role of removing light of unnecessary wavelengthssuch as infrared light and wave-filtering optical false signals. Usingan example of an optical low pass filter, commonly used configurationsof such optical filters include configurations in which plates such as aquartz birefringent plate and an infrared cut glass plate areappropriately combined according to desired wave-filteringcharacteristics. And in recent years, depending on an application,configurations in which an optical interference film is formed on asingle plate are also being used. In the case of a configuration inwhich a plurality of plates are combined, conventionally manufacture ofsuch optical filters involved using an adhesive to individually laminatethe optical plates to be combined, which were divided into small pieces.

However, in recent years, as shown in JP H9-43542A for example, aso-called multi-cutout manufacturing method has been proposed andimplemented, which involves laminating necessary structural membersaccording to required wave-filtering characteristics at a stage prior tocutting of the wafer into small pieces, then performing cutting toobtain individual optical filters. Reductions in manufacturing costshave been achieved with manufacturing methods such as this.

On the other hand, cut edge portions of an optical filter made with thismulti-cutout manufacturing method are sharp. These edge portions areoften cracked or chipped when viewed microscopically, and there is apossibility that some of the optical plates will suffer from furtherchipping or cracking. In this case, cracked pieces or chipped pieces mayadhere to a main surface of the optical plate, which is a transmissionsurface for optical information, and become optical foreign substances.Such foreign substances may be picked up by image-taking elements suchas a CCD and become a cause of worsened image quality during videooutput.

Furthermore, other members may be cut when the edge portions are sharpand such cut pieces can become optical foreign substances. For example,it is common for optical filters to be storage packed in a resin casefor delivery to a customer, and edge portions can cut into an inner wallof the resin case due to looseness within the storage case, thusresulting in cut pieces adhering to a main surface of an optical plate.Configurations have been disclosed with regard to preventing suchlooseness, such as JP 2000-238877A, in which side surfaces of an opticalfilter are fixedly supported, and JP 2001-2167A, in which the opticalfilter is fixed with an adhesive sheet. However, optical foreignsubstances also can be produced by contact with a case when opticalfilters are taken out from the case to be moved individually.

As a countermeasure against such optical foreign substances, JapaneseUtility Model No. 2508176 discloses a configuration in which chamferingthat forms a linear slanted surface is performed with respect to edgesformed on an optical filter. Although such a chamfered structure is notsharp, edges are still formed, and these edge portions may be affectedby cracking or chipping, thus resulting in pieces being cut from a resincase as mentioned above.

And furthermore, due to continued miniaturization of image-takingdevices such as video cameras, a distance between a front surface of aCCD and an optical filter positioned thereon has been becoming shorterin recent years. And in this case, optical foreign substances that haveadhered to a main surface of the optical filter cause even moreconspicuous image defects, leading to worsened image quality duringvideo output.

SUMMARY OF INVENTION

The present invention has been devised in light of these technologicaltrends, and it is an object therein to provide a high quality opticalfilter that can greatly suppress occurrence of optical foreignsubstances in optical filters and a method for manufacturing such anoptical filter, as well as to provide a storage structure that canmaintain a quality of the optical filter.

In order to achieve the above-mentioned object, the present inventionforms fewer edges and greatly suppresses occurrence of optical foreignsubstances by performing curve chamfering for the optical filter, andcan therefore solve these issues with the following configurations.

First, an optical filter according to the present invention is providedwith one or a plurality of optical plates, wherein curve chamfering isperformed on an edge of at least a side surface side of the opticalfilter. This curve chamfering may be performed on an edge of one mainsurface side of the optical filter, or may be performed on edges of bothmain surface sides of the optical filter, it may be performed on a sidesurface side and one main surface side or on a side surface side andboth main surface sides.

Here, chamfering of an edge of a main surface side refers to chamferingan edge (sides enclosing a main surface) formed on a main surface side.A result of performing this chamfering is that the optical filter isground across a main surface and a side surface. Furthermore, chamferingof an edge of a side surface refers to chamfering an edge formed betweenadjoining side surfaces. A result of performing this chamfering is thata side surface of the optical filter is ground.

As curve chamfering is performed on an edge of at least a side surfaceside of the optical filter, cracking or chipping of an optical platethat occurs conventionally is greatly suppressed, and cutting debristhat occurs by contact with a case or other portions is also greatlyinhibited, and occurrence of optical foreign substances as a whole issuppressed. Therefore, adherence of such optical foreign substances to amain surface of the optical filter is eliminated.

Furthermore, in a case of performing curve chamfering on only one mainsurface, it is easy to chamfer by preparing a form of a dicing blade tocut a wafer into individual small pieces of optical filters after thewafer has been laminated to obtain desired wave-filteringcharacteristics. It should be noted that, as mentioned above, theshorter the distance between the CCD and an optical foreign substance,the more conspicuous is image deterioration. Consequently, whenperforming curve chamfering on only one main surface, it is preferablethat the main surface that is curve chamfered so as to have an effectthat suppresses occurrence of optical foreign substances is set on aside of an image-taking element. It should be noted that when curvechamfering is performed on both main surfaces, there is no need todiscriminate placement direction in this way.

Next, in configurations in which curve chamfering is performed onoptical plates that make up an optical filter, it is required that eachindividual optical plate is chamfered. Such a configuration is the sameas the above-mentioned curve chamfering of the optical filter.

That is to say, it is characterized by curve chamfering being performedon an edge of at least a side surface side of each optical plate. Thiscurve chamfering may be performed on an edge of one main surface side ofeach optical plate, or may be performed on an edge of both main surfacesides of each optical plate, or may be performed on an edge of a sidesurface side and one main surface side of each optical plate, or on aside surface side and both main surface sides of each optical plate.

With these configurations it is also possible to greatly suppressoccurrence of optical foreign substances.

In the above configurations, in the curve chamfering of the edge of themain surface side, an amount of chamfering on a main surface side may besmaller than an amount of chamfering on a side surface side. In thepresent invention, “chamfering amount” refers to an amount prescribed bya predetermined chamfering width and a curvature by which an amount of aground optical filter is defined.

With these configurations, it is also possible to greatly reduceoccurrence of optical foreign substances since edges are not formed, andby reducing a width of chamfering on a main surface side, an area ofactual optical information transmission on the main surface can be keptbroad, which greatly contributes to suppression of image deteriorationparticularly in regard to recent rapid advances in miniaturization ofimage-taking devices such as video cameras.

Furthermore, in the curve chamfering of the edges of the main surfaceside, an amount of chamfering on one main surface side may be smallerthan an amount of chamfering on another main surface side.

With this configuration, it is possible to identify a front and back ofan optical filter using differences between these curvatures, not onlyvisually, but also by sense of touch. It is also possible to performthis identification using a screen recognition device.

A method for manufacturing an optical filter as described above includesa step of cutting a layered optical wafer, which has been formed as asingle optical wafer or a plurality of layered optical wafers that canbe cut into a plurality of optical plates, into small pieces using adicing blade so that divided surfaces of the optical wafer are parallel,and a step of curve chamfering the layered optical wafer using a curvedsurface blade having a curved surface whose curvature corresponds to arequired curve at a position of an edge to be curve chamfered. In thisconfiguration, an order of cutting the wafer and curve chamfering is nota concern, and either may be performed first.

When curve chamfering is formed on both surfaces of an optical filter,it is possible to perform curve chamfering on one surface side withpredetermined spacing with a blade having a curved surface portion, tothen turn the optical filter over and fix it, and to then form curvedportions and perform cutting into small pieces after making the requiredpositional adjustments. A blade used for cutting into small pieces is adisk-shaped dicing blade for example, and performs cutting whilerotating at high speed.

Furthermore, as another manufacturing method, after a layered opticalwafer is formed, a blade is used that is provided with a dicing bladeportion with which divided surfaces of the optical wafer become parallelto one another, and a curved surface blade portion that has a curvedsurface corresponding to a curvature of an edge to be curve chamfered,and the layered optical wafer is cut into small pieces with the dicingblade portion, after which curve chamfering is performed with the curvedsurface blade portion on an edge of the layered optical wafer that hasbeen cut into small pieces.

With this manufacturing method, since the above-described blade is used,it is possible to perform processes for cutting into small pieces andcurve chamfering for edges of an optical filter continuously, which isefficient.

In a further manufacturing method, after a layered optical wafer isformed, the layered optical wafer is cut into small pieces using adicing blade so that divided surfaces of the optical wafer are parallel,and an edge of the layered optical wafer that has been cut into smallpieces is curve chamfered by grinding with a grinding device positionedin a position facing a grinding curved surface corresponding to acurvature to be curve chamfered.

These grinding surfaces positioned on opposite sides may have the samecurvature or may have different curvatures. When a spacing of thegrinding surfaces is formed matching a thickness of the optical filter,it is possible to perform curve chamfering on two edges in one step.Furthermore, when a configuration is used in which the spacing of thegrinding surfaces has a width, thicknesses of the optical filters do nothave to be uniform and may be adapted to optical filters of variousthicknesses.

Moreover, a storage structure for storing an optical filter according tothe present invention is provided with a storage case that has a recessportion for storing the optical filter, wherein an inclined surface isformed at an inner peripheral surface of the recess portion across aside surface and bottom surface therein, and wherein the optical filteris stored in a state in which a curve chamfered portion of the opticalfilter is in contact with the inclined surface.

With this storage structure, the optical filter is held in a state inwhich its curve chamfered portions are in contact with inclined surfaceportions of the storage case, and in this case, since curve chamferinghas been performed on the optical filter, edge portions of the opticalfilter do not make contact in a sharp condition, which allows occurrenceof optical foreign substances to be suppressed.

Further still, an optical device according to the present invention isprovided with an image-taking element and a package for accommodatingthe image-taking element, wherein an opening portion is formed in thepackage, and wherein an optical filter of the present invention isarranged at the opening so as to cover the opening portion.

With an optical device of the above-described configuration, the openingportion of the package is covered by the optical filter, and thisoptical filter has a usual function of being a light transmission memberand is also provided with a sealing function for the package. Thisoptical filter is curve chamfered on its main surface sides and/or itsside surface sides, and therefore, as described above, the opticalfilter itself does not produce chips, and there are almost no opticalforeign substances since the optical filter does not cut the package.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing an embodiment of an optical filteraccording to the present invention.

FIG. 2 is an enlarged view of a portion indicated by arrow RA in FIG. 1.

FIG. 3 is a side view showing another embodiment of an optical filteraccording to the present invention.

FIG. 4 is a side view showing a further embodiment of an optical filteraccording to the present invention.

FIG. 5 is a side view showing yet a further embodiment of an opticalfilter according to the present invention.

FIG. 6 is a side view showing yet a further embodiment of an opticalfilter according to the present invention.

FIG. 7 is a side view showing yet a further embodiment of an opticalfilter according to the present invention.

FIGS. 8( a) and 8(b) show yet a further embodiment of an optical filteraccording to the present invention, with FIG. 8( a) showing a top viewof a main surface and FIG. 8( b) showing a side view thereof.

FIGS. 9( a) and 9(b) show yet a further embodiment of an optical filteraccording to the present invention, with FIG. 9( a) showing a top viewof a main surface and FIG. 9( b) showing a side view thereof.

FIG. 10 is a top view showing a main-surface side of yet a furtherembodiment of an optical filter according to the present invention.

FIG. 11 is a top view showing a main-surface side of yet a furtherembodiment of an optical filter according to the present invention.

FIG. 12 is a side view showing yet a further embodiment of an opticalfilter according to the present invention.

FIG. 13 is a diagram illustrating an embodiment of a method formanufacturing an optical filter according to the present invention.

FIG. 14 is a diagram illustrating an embodiment of another method formanufacturing an optical filter according to the present invention.

FIG. 15 is a diagram illustrating a grinding device used in a method formanufacturing an optical filter according to the present invention.

FIG. 16 is a diagram for describing another grinding device used in amethod for manufacturing an optical filter according to the presentinvention.

FIG. 17 is a diagram for describing a further grinding device used in amethod for manufacturing an optical filter according to the presentinvention.

FIG. 18 is a cross section of a storage structure for an optical filteraccording to the present invention.

FIG. 19 is a cross section of a further storage structure for an opticalfilter according to the present invention.

FIG. 20 is a view of an overall configuration of an image-taking devicein which an optical filter according to the present invention is used.

FIG. 21 is a view of an overall configuration of another image-takingdevice in which an optical filter according to the present invention isused.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, an embodiment of an optical filter according to the presentinvention is described using an optical low pass filter as an examplewith reference to the accompanying drawings. FIG. 1 is a side viewshowing an embodiment of an optical filter according to the presentinvention.

FIG. 2 is an enlarged view of a portion indicated by arrow RA in FIG. 1.

An optical low pass filter 10 is constituted by a quartz birefringentplate 11, a quarter wavelength plate 12, and a quartz birefringent plate13 layered in that order. The quartz birefringent plates 11 and 13 use abirefringence effect of quartz to output outgoing beams by separatingincident light into ordinary rays and extraordinary rays, and adirection and width of these separated beams can be adjusted asappropriate with predetermined parameters. In this way, an optical lowpass filter is constituted by combining quartz birefringent plates andthe like as appropriate. The quartz birefringent plate 11 is set, forexample, to separate rays in a horizontal direction, and has a functionof separating incident light in the horizontal direction using abirefringence effect of quartz. Furthermore, an anti-reflection coating14 is formed on an incident light surface (main surface) of the quartzbirefringent plate 14. Although not shown in detail in the drawings, theanti-reflection coating 14 is formed by multi-layering dielectric thinfilms made of metal oxide films or the like. On the other hand, thequartz birefringent plate 13 is set, for example, to separate rays at a90 degree angle, and has a function of splitting incident light in a 90degree direction using a birefringence effect of quartz. Furthermore, aninfrared cut coating 15 is formed on an outgoing light surface (mainsurface) of the quartz birefringent plate 13. Although not shown indetail in the drawings, the infrared cut coating 15 is also formed bymulti-layering dielectric thin films.

Curved chamfered portions 13 a and 13 b are formed at a periphery of theoutgoing light surface (main surface) of the quartz birefringent plate13. As shown in FIGS. 1 and 2, this curved chamfering is a formation inwhich edge portions are chamfered to a curved condition, and chamferingof a main surface-side edge is configured with a predetermined curvatureso that an amount of chamfering on the main surface-side edge is lessthan the amount of chamfering on a side surface-side edge. That is,chamfering width t2 on the main surface-side shown in FIG. 2 is shorterthan chamfering width t1 on the side surface side. With such aconfiguration, since edges are not formed as compared with conventionalstraight chamfering, occurrence of optical foreign substances caused bycracking or chipping of the optical filter can be reduced, and it isalso possible to greatly inhibit occurrence of optical foreignsubstances caused by edge portions cutting into a packaging case or thelike. Moreover, by reducing the width of chamfering on the main surfaceside, an area of actual optical information transmission on the mainsurface can be kept broad, thus reducing loss of optical information.The present invention can suppress image deterioration particularly withregard to recent rapid advances in miniaturization of image-takingdevices such as video cameras.

The above embodiment described a configuration in which only one mainsurface was curve chamfered, but an optical low pass filter 30, as shownin FIG. 3, in which both main surfaces are curve chamfered is alsopossible. The optical low pass filter 30 is constituted by abirefringent plate 31, an infrared cut filter 32, a phase differenceplate 33, and a birefringent plate 34 layered in that order, with curvechamfering performed on the birefringent plates 31 and 34, which arepositioned as two main surfaces of the optical low pass filter 30, thusforming curve chamfered portions 31 a, 31 b, 34 a, and 34 b.

Furthermore, optical low pass filters 40 and 50 shown in FIGS. 4 and 5are each constituted by a single optical plate 41 and 51. The opticallow pass filter 40 is configured with curve chamfered portions 41 a and41 b formed on one main surface side, and the optical low pass filter 50is configured with curve chamfered portions 51 a, 51 b, 51 c, and 51 dformed on both main surface sides.

Moreover, as shown in FIG. 6, an optical low pass filter 60 is formedwith two layered optical plates 61 and 62, and may have curve chamferedportions 61 a, 61 b, 62 a, and 62 b formed on both main surface sides.

Also, as shown in FIG. 7, an optical low pass filter 70 is formed withthree layered optical plates 71, 72, and 73, and may have curvechamfered portions 71 a to 71 d, 72 a to 72 d, and 73 a to 73 d formedon both main surface sides of each of the optical plates 71, 72, and 73.

And moreover, similar to FIGS. 4 and 5, an optical low pass filter 80 asshown in FIG. 8 is made of a single optical plate 81. Curve chamferingis performed on side surface sides, thereby forming curve chamferedportions 81 a to 81 d. And very finely chamfered portions 82 a areformed on a main surface side.

As a configuration in which curve chamfering is performed on the sidesurface sides, there is also a configuration in which curve chamferingis also performed on the main surface side, as shown in FIGS. 9( a) and9(b). An optical low pass filter 90 is made of a single optical plate91, with curve chamfered portions 91 a to 91 d on the side surface sidesand curve chamfered portions 91 e to 91 h on the main surface sides, sothat the optical low pass filter 90 has no edges on any surface, and isthus a configuration which has the least contact-related damage.

It should be noted that, although not shown in the drawings, opticalfilters made of one or a plurality of optical plates according to thepresent invention may also be configured so that curve chamfering isperformed on a side surface and one main surface side.

Any of the optical filters according to the present invention may beprovided as required with an infrared cut coating or an anti-reflectioncoating or the like on a main surface of an optical plate.

The optical filters according to the present invention have been createdfocusing on a perspective of a shape of the optical filters, such thatany impact at a time of contact is reduced in order to inhibitoccurrence of optical foreign substances, but since a nature of asurface itself can be thought of as a cause of optical foreignsubstances that must be overcome in order to further inhibit occurrenceof optical foreign substances, it is preferable to apply the presentinvention after making considerations as appropriate to the nature ofthe surface.

Furthermore, as shown in the configurations of the optical filters shownin FIGS. 1 through 11, it is preferable that flat areas are formed onthe side surfaces or that flat areas are left there when curvechamfering is performed. A basis for this is explained using acomparison with a case of all side surfaces being formed as roundshapes. First, a micrometer or the like is used when measuring outerdimensions, and such dimensional measurements become difficult when allside surfaces are formed as round shapes, and thus there is an advantageof ease of measurement when flat areas are formed on the side surfaces.Moreover, when all side surfaces are formed as round shapes, it isnecessary to prepare diamond wheels with different radial dimensions fordiamond wheels used in curve chamfering processes and grinding processesin accordance with a thickness of a workpiece (optical plate). Incontrast to this, even when there are differences in thicknesses of theworkpiece (optical plate), it is possible to use the same single diamondwheel of a radial dimension that can be used for all the flat areas,thus increasing a range over which tools can be used in manufacturing.

Furthermore, it is possible to clearly indicate a separation directionof incident light on a birefringent plate by varying widths of curvechamfering.

For example, with an optical filter 100 shown in FIG. 10, it is possibleto clearly indicate a direction of light separation by making curvechamfered portions 104 and 105, which are curve chamfered edges ofopposing sides, larger than curve chamfered portion 103 (t4=t5, t4>t3).Moreover, with an optical filter 110 shown in FIG. 11, it is possible toclearly indicate a direction of light separation by making curvechamfered portion 114, which is a wide curve chamfered edge of one side,larger than curve chamfered portion 113 (t6<t8<t7).

As a configuration in which a width of curve chamfering is varied, anoptical filter 120 as shown in FIG. 12 is possible in which an amount ofcurve chamfering on edges of one main surface side is smaller than anamount of curve chamfering on edges of another main surface side. In thepresent embodiment, curve chamfering is performed respectively on fouredges of each main surface. The following is a description of thepresent embodiment based on the accompanying drawings.

With the optical filter 120, curve chamfered portions 121 a and 121 b ofedges of a main surface 121A of the optical plate 121 are chamfered tohave an equivalent curvature. On the other hand, curve chamferedportions 121 c and 121 d of edges of a main surface 121B are chamferedto have an equivalent curvature and so as to have a different curvaturefrom the curve chamfered portions 121 a and 121 b of the edges of themain surface 121A. In this embodiment, chamfering width s2 of the edgesof the main surface 121A is smaller than chamfering width s1 of theedges of the main surface 121B (s2<s1).

With the optical filter 120 it is possible to identify a front and backof the optical filter 120, not only visually, but also by sense oftouch. It is also possible to perform this identification using a screenrecognition device. In a coating process that will be discussed laterbelow, it is necessary to apply a coating to only one main surface onone side, and in this case it is extremely important to be able toperform front and back identification accurately and with ease. Andbecause such identification is particularly difficult when opticalfilters are thin, by using different amounts of chamfering for one mainsurface and the other main surface as in the present configuration, thatis, by making a curvature of the curve chamfering performed on each mainsurface different, it is easy to identify the front and back of theoptical filter.

The following is a description of a method for manufacturing an opticalfilter according to the present invention.

As mentioned earlier, a multi-cutout manufacturing method has often beenused in recent years from a point of view of reducing manufacturingcosts. FIG. 13 shows an embodiment in which a method for manufacturingan optical filter according to the present invention has been applied ina multi-cutout manufacturing method.

In the multi-cutout manufacturing method, at a stage before a wafer iscut into small pieces, necessary structural members are laminatedaccording to required wave-filtering characteristics. That is, anoptical filter wafer 8 can be obtained, for example, by bonding in ordera quarter wavelength plate wafer 8 b and a birefringent plate wafer 8 c,which separates light perpendicularly, on a birefringent plate wafer 8a, which separates light horizontally.

Next, the optical filter wafer 8 is cut into predetermined small piecesby a blade 120 while, for example, the wafer is temporarily fixed on asupport stand 9 by an adhesive. The blade 120 used is a disk-shapeddicing blade. As shown in FIG. 13, viewed in cross section, the blade120 has a small width and is provided with a chamfering blade portion122 that has a parallel cutting portion 121, a planar shape of which iscircular, and a curved surface portion 122 a, which is formed at aninner portion of this circular shape. The curved surface portion 122 ais formed with a curved surface in accordance to a curvature required tochamfer edge portions of the optical filter to a predeterminedcurvature. Slicing (arrow Y1) is performed to a depth proximal to a tipportion of the curved surface portion 122 a while rotating (arrow R1)the blade 120 at high speed to cut the optical filter wafer 8 into amatrix shape. In this way, cut surfaces of the wafer become sidesurfaces of the optical filter 10, and a curve chamfered portion 13 a isformed on one main surface side of the optical filter 10. After this,the adhesive is dissolved, and individual optical filters 10 areseparated. It should be noted that a shape of curve chamfering can becontrolled using a shape of the curved surface portion 122 a of theblade 120.

Furthermore, as shown in FIG. 2 for example, in regard to chamfering ofedges of a main surface, when a chamfering width of a main surface sideis smaller than a chamfering width of a side surface side, a radiallength of the blade 120 becomes relatively longer due to the shape ofthe curved portion 122 a, and the curved portion 122 a as a whole is asharp shape along the parallel cutting portion 121.

FIG. 14 is a diagram for describing another embodiment of a method formanufacturing an optical filter according to the present invention.

A step cutting method is employed in this embodiment using two types ofblades as shown in FIG. 14.

First, as in the previous embodiment, at a stage before a wafer is cutinto small pieces, necessary structural members are laminated accordingto required wave-filtering characteristics. That is, optical filterwafer 8 can be obtained by bonding in order quarter wavelength platewafer 8 b and birefringent plate wafer 8 c, which separates lightperpendicularly, on birefringent plate wafer 8 a, which separates lighthorizontally.

Next, the optical filter wafer 8 is cut into predetermined small piecesby a flat blade 132 while the wafer is adhered to support stand 9 by anadhesive. The blade used is a disk-shaped dicing blade and, as shown inFIG. 14, when viewed in cross section, the blade is made of only afine-width parallel cutting portion. Edge portions of optical filter 10are chamfered to a predetermined curvature with a chamfering blade 131.The chamfering blade 131 used in this process is formed with a curvaturecorresponding to an applicable curvature. After this, the adhesive isdissolved, and individual optical filters 10 are separated from thesupport stand 9. Curve chamfering is performed after cutting into smallpieces in this manufacturing method, but it is also possible to firstperform curve chamfering using the chamfering blade 131 and then toperform cutting into small pieces using the flat blade 132.

Furthermore, it is also possible to set in advance a spacing betweenthese blades and perform parallel cutting with a predetermined spacingafter adjusting the blades to a required height (slicing depthadjustment).

Moreover, it is also possible to perform cutting by a multi-bladeconfiguration with the same type of blades positioned in parallel.

The present embodiment was described using a case in which curvechamfering was performed on only one surface of the optical filter, butwhen manufacturing optical filters such as those shown in FIGS. 3, 5, 6,7, and 9, or when manufacturing optical filters of a configuration inwhich chamfered portions are formed on both main surfaces of an opticalplate, a method can be executed in which curve chamfering is performedon one main surface by cutting a portion of optical filter wafer 8 withthe chamfering blade 131 used in the manufacturing method shown in FIG.14 for example, then turning the optical filter wafer 8 over andadhesively fixing it and performing curve chamfering again by cuttingwith the blade 120 used in FIG. 13 after making required positionaladjustments.

In the above-described manufacturing method, it is also possible to usea grinding tool 5 as shown in FIG. 15 when performing curve chamferingon edges of an optical filter. The grinding tool 5 is formed so that across section of a diamond wheel for performing curve chamfering onedges of optical filter 1 has a U-shaped grooved surface, and isconfigured so that opposite curved surfaces 5 a and 5 b are ground to apredetermined curvature. The grinding tool 5 is provided with a grindingsurface that has the same curvature.

Grinding is performed in this grinding process by bringing the curvedsurface 5 a or 5 b of the grinding tool into contact with apredetermined surface of the optical filter 1. It is possible to movethe optical filter 1 in a direction of arrow X1, and a thickness of theoptical filter 1 can be adapted to various widths within a distance inwhich movement is possible, which offers better usability since a widthb can be applied to a thickness of the optical filter 1 to be curvechamfered.

Furthermore, when it is desired to vary a curve of opposite curvedsurfaces, it is possible to use a grinding tool 6 that has curvedsurfaces 6 a and 6 b with different curvatures as shown in FIG. 16. Alsoin this case, grinding can be performed with the same method as in FIG.15.

Furthermore, when not curve chamfering in order on each edge by movingthe optical filter as shown in FIG. 15 or FIG. 16, but insteadperforming curve chamfering simultaneously on edges of both mainsurfaces, it is possible to use a grinding tool 7 as shown in FIG. 17for example. As in FIGS. 15 and 16, this grinding tool 7 is formed witha diamond wheel forming a grooved surface, a cross section of which isU-shaped. A width into which an optical filter to be curve chamfered canbe fit into the grinding tool 7 is a point of difference between thegrinding tool 7 and the grinding tools 5 and 6. The U-shaped curvedgrinding surface is moved in a direction of arrow Y2 so that opticalfilter 1 is fit into it and curve chamfering is performed. Curvechamfering of both main surfaces can be performed simultaneously whenusing the grinding tool 7, which makes this tool superior in terms ofoperational efficiency.

After an optical filter has been cut into small pieces and undergoneperipheral processing (curve chamfering) of the methods shown in FIGS.13 through 17, portions of side surfaces of the optical filter that havebeen made rough are smoothened by wet etching after rinsing. An etchingsolution used in this process is a mixed solution of ammonium fluoride,hydrofluoric acid, and the like. Rinsing is performed after thisprocess, then thicknesses of main surfaces are adjusted to apredetermined thickness with a secondary grinding process. After furtherrinsing, the main surfaces of the optical filter are given a mirrorfinish by performing a polishing-grinding process. Then, after furtherrinsing, a main surface that is to become an optical surface is given acoating film. When main surface sides of the optical filter are givendifferent curvatures with curve chamfering as shown in FIG. 12 forexample, it is easy to identify the main surface for coating in thisprocess, which is another advantage of a configuration in whichchamfering for curves are varied.

The following is a description of a configuration for storing an opticalfilter according to the present invention manufactured by theabove-described manufacturing method.

Since an optical filter is stored in a case in a condition in which asurface for incoming optical information is exposed, it is necessary tothoroughly eliminate optical foreign substances. FIG. 18 is a crosssection of a storage structure in which optical filters 15 and 16 arestored in a storage case 17.

The storage case 17 has storage recess portions 171 and 174 for storingthe optical filters 15 and 16. Inclined surface portions 172 and 173(175 and 176) are incorporated continuously in a base peripheral portionof each storage recess portion 171 (174). Curve chamfered portions 151and 152 (161 and 162) formed respectively on one main surface side ofthe optical filter 15 (16) are brought into contact respectively withthe inclined surface portions 172 and 173 (175 and 176) and arehorizontally mounted and stored in the storage case 17 in this state.With this storage structure, storage is achieved without any acute anglecontact between the curve chamfered portions 151 and 152 (161 and 162)of the optical filter 15 (16) and the inclined surface portions 172 and173 (175 and 176) of the storage case 17, thus enabling suppression ofoptical foreign substances caused by contact with the storage case 17.

This storage structure is an embodiment in which the optical filters arelaid flat with their main surface facing up, but the following is adescription of yet another embodiment in which an optical filter isstood on its side surface portions as shown in FIG. 19.

As in the above-described embodiment, a storage recess portion 210 isformed in this storage structure for storing optical filter 15 in astorage case 20. Inclined surface portions 201 and 202 are formed in aperipheral base portion of the storage recess portion 210. The opticalfilter 15, side surface edges of which are chamfered to form curvechamfered portions 153, 154, 155, and 155, is stood on its side surfaceportions for storage in the storage recess portion 210. That is, thecurve chamfered portions 153 and 154 are respectively held by beingbrought into contact with the inclined surface portions 201 and 202 ofthe storage case 20. With this storage structure too, storage isachieved without any acute angle contact between the curve chamferedportions 153 and 154 of the optical filter 15 and the inclined surfaceportions 201 and 202 of the storage case 20, thus enabling suppressionof optical foreign substances caused by contact with the storage case20.

Moreover, a press-down plate 25 may be latched and fixed to the storagecase 20 to stably hold the optical filter 15. A pressing portion 25 a isprovided at the press-down plate 25 and presses an upper side surface 15a of the optical filter 15 while the filter is fixed. The pressingportion 25 a is formed as a curved surface and is made of a materialthat has cushioning properties. Accordingly, when the press-down plate25 is fixed to the storage case 20, the pressing portion 25 a causes nodamage to the optical filter 15.

In the above-described storage structure, it is also possible that astructure of the inclined surface portions of the storage case do nothave a constant inclined surface, but rather have a concave curvature ora convex curvature for example.

It should be noted that the present embodiment was described for astorage case having two storage recess portion holes, but it is alsopossible to use a storage case in which a multitude of storage recessportions are formed in a matrix shape, and it is also possible to use aconfiguration in which multiple tiers of such storage cases are stacked.

When used in an image-taking device, since the optical filter accordingto the present invention has no edges after undergoing curve chamferingas described above, chips or other debris of the optical filter are notproduced, and therefore there are almost no optical foreign substancesproduced from the optical filter itself. Furthermore, this enablesoccurrence of optical foreign substances due to cutting of the CCDpackage by the optical filter to be suppressed. FIGS. 20 and 21 areviews of overall configurations of examples of image-taking devices inwhich optical filters according to the present invention are used.

An image-taking device 180 shown in FIG. 20 is provided with a CCDpackage 185 made of ceramic, and a CCD 182 is mounted in a recessportion provided in the CCD package 185 so that an opening portion ofthe recess portion is covered by an optical filter 181. The opticalfilter 181 is mounted on a step 183 provided on an inside surface of therecess portion. The optical filter 181 is configured such that both mainsurface sides and side surface sides have undergone curve chamfering.Accordingly, as described above, the optical filter 181 is preventedfrom producing chips or other debris, and since there is no cutting ofthe CCD package 185 by the optical filter 181, there are almost nooptical foreign substances produced. Moreover, since the opening portionof the recess portion is covered by the optical filter 181, this alsoperforms a role of providing the CCD package 185 with sealingproperties.

Furthermore, a configuration of a CCD package 195 of an image-takingdevice 190 shown in FIG. 21 is different from the configuration shown inFIG. 20. The CCD package 195 is formed with members 95 a forming a sidewall attached to a member 95 b, which forms a base portion. Upperportions of the members 95 a are formed with protruding portions 951that protrude inward so as to enclose an opening portion of the CCDpackage 195. Optical filter 181 is fixed with an adhesive to inner sidesof the protruding portions 951 as well as to side surfaces 952 of themembers 95 a, and this also performs a role of providing CCD package 195with sealing properties.

As described above, due to continued miniaturization of image-takingdevices such as video cameras, a distance between a CCD and an opticalfilter has been becoming shorter in recent years, so that adherence ofoptical foreign substances to the optical filter has become an evenworse image defect. An optical filter according to the present inventionis superior in that it solves this issue and is beneficial as astructure that thoroughly eliminates occurrence of optical foreignsubstances. A method by which optical filters of this structure can bemanufactured is also beneficial and, from a perspective of being able tomaintain quality of such a high quality optical filter, a structure canbe provided for storing a thus-manufactured optical filter.

1. An optical filter comprising one or a plurality of optical plates,the optical filter having a first main surface, a second main surface,and a plurality of side surfaces connecting the first main surface andthe second main surface, wherein a side surface edge formed by adjacentside surfaces of the optical filter is chamfered with a curvature toform a curved chamfered portion, wherein a first main surface edgeformed by the first main surface and at least one of the side surfacesof the optical filter is chamfered with a curvature to form a curvedchamfered portion, and wherein, at the first main surface edge, a widthof the curved chamfered portion along the first main surface is lessthan a width of the curved chamfered portion along each of the at leastone of the side surfaces.
 2. An optical filter according to claim 1,wherein a second main surface edge formed by the second main surface andat least one of the side surfaces of the optical filter is chamferedwith a curvature to form a curved chamfered portion.
 3. An opticalfilter comprising a plurality of optical plates, each of the opticalplates having a first main surface, a second main surface, and sidesurfaces connecting the first main surface and the second main surface,wherein a side surface edge of a first optical plate formed by adjacentside surfaces of the first optical plate is chamfered with a curvatureto form a curved chamfered portion, wherein a first main surface edgeformed by the first main surface of the first optical plate and at leastone of the side surfaces of the first optical plate is chamfered with acurvature to form a curved chamfered portion, and wherein, at the firstmain surface edge, a width of the curved chamfered portion along thefirst main surface is less than a width of the curved chamfered portionalong each of the at least one of the side surfaces.
 4. An opticalfilter according to claim 3, wherein a second main surface edge formedby the second main surface of the first optical plate and at least oneof the side surfaces of the first optical plate is chamfered with acurvature to form a curved chamfered portion at a periphery of thesecond main surface.
 5. An optical filter comprising one or a pluralityof optical plates, the optical filter having a first main surface, asecond main surface, and one or more side surfaces connecting the firstmain surface and the second main surface, wherein a first main surfaceedge formed by the first main surface and at least one side surface ofthe optical filter is chamfered with a curvature to form a curvedchamfered portion at a periphery of the first main surface, wherein asecond main surface edge formed by the second main surface and at leastone side surface of the optical filter is chamfered with a curvature toform a curved chamfered portion at a periphery of the second mainsurface, and wherein a width of the curved chamfered portion along thefirst main surface at the first main surface edge is smaller than awidth of the curved chamfered portion along the second main surface atthe second main surface edge.
 6. An optical filter according to claim 5,wherein the one or more side surfaces comprise three or more sidesurfaces.
 7. An optical filter comprising one or a plurality of opticalplates, said optical filter having a first main surface, a second mainsurface, and side surfaces connecting the first main surface and thesecond main surface, wherein a side surface edge formed by adjacent sidesurfaces of the optical filter is chamfered with a curvature to form acurved chamfered portion, wherein a first main surface edge formed bythe first main surface and at least one of the side surfaces of theoptical filter is chamfered with a curvature to form a curved chamferedportion at a periphery of the first main surface, wherein a second mainsurface edge formed by the second main surface and at least one of theside surfaces of the optical filter is chamfered with a curvature toform a curved chamfered portion at a periphery of the second mainsurface, and wherein a width of the curved chamfered portion along thefirst main surface at the first main surface edge is smaller than awidth of the curved chamfered portion along the second main surface atthe second main surface edge.
 8. An optical filter comprising aplurality of optical plates, each of the optical plates having a firstmain surface, a second main surface, and one or more side surfacesconnecting the first main surface and the second main surface, wherein afirst main surface edge formed by the first main surface of a firstoptical plate and at least one side surface of the first optical plateis chamfered with a curvature to form a curved chamfered portion at aperiphery of the first main surface of the first optical plate, whereina second main surface edge formed by the second main surface of thefirst optical plate and at least one side surface of the first opticalplate is chamfered with a curvature to form a curved chamfered portionat a periphery of the second main surface of the first optical plate,and wherein a width of the curved chamfered portion along the first mainsurface at the first main surface edge is smaller than a width of thecurved chamfered portion along the second main surface at the secondmain surface edge.
 9. An optical filter according to claim 8, whereinthe one or more side surfaces comprise three or more side surfaces. 10.An optical filter comprising a plurality of optical plates, each of theoptical plates having a first main surface, a second main surface, andone or more side surfaces connecting the first main surface and thesecond main surface, wherein a side surface edge of a first opticalplate formed by adjacent side surfaces of the first optical plate ischamfered with a curvature to form a curved chamfered portion, wherein afirst main surface edge formed by the first main surface of the firstoptical plate and at least one of the side surfaces of the first opticalplate is chamfered with a curvature to form a curved chamfered portionat a periphery of the first main surface, wherein a second main surfaceedge formed by the second main surface of the first optical plate and atleast one of the side surfaces of the first optical plate is chamferedwith a curvature to form a curved chamfered portion at a periphery ofthe second main surface, and wherein a width of the curved chamferedportion along the first main surface at the first main surface edge issmaller than a width of the curved chamfered portion along the secondmain surface at the second main surface edge.